Comprehensive functional mapping of accessory chromosomes identifies a dominant virulence-regulator paralog in tomato wilt pathogen
Accessory chromosomes (ACs) serve as flexible genomic compartments that facilitate rapid adaptive evolution in eukaryotic microbes. In the tomato wilt pathogen Fusarium oxysporum f. sp. lycopersici, ACs are essential for virulence and host specificity; however, their structural complexity and functional redundancy have hindered a systematic characterization of their distinct roles. Here, we…
Recent research has uncovered a critical virulence-regulator paralog in the tomato wilt pathogen, Fusarium oxysporum f. sp. lycopersici. This discovery sheds light on how accessory chromosomes play a crucial role in the rapid adaptive evolution of eukaryotic microbes. The scientists employed a CRISPR/Cas9-based platform to systematically dissect the functional roles of these accessory chromosomes.
By generating a library of 36 large deletion mutants across a 10 megabase putative AC region, they were able to identify seven segments essential for complete virulence towards tomato. Among these, FTF1a-1 emerged as the dominant regulator of virulence, originating from the duplication of a core-chromosomal virulence gene into the accessory chromosome region.
Interestingly, the FTF1a-3 paralog showed minimal contribution to virulence, while other paralogs had no significant impact on disease development. The study reveals a functional hierarchy within the duplicated FTF1 gene family, highlighting how neofunctionalization of virulence genes can lead to hyper-virulence and host-specific adaptation in F. oxysporum.
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